The present invention pertains generally to valves used in high pressure systems where substantial loads are applied to the movable element of the valves.
In valves controlling fluid flows above 1000 PSI a problem exists by reason of the movable valve member being heavily biased, often by pressure in a downstream line, against a surface of the valve body. Accordingly, considerable torque may be required to position the plug member or other movable member of the valve. Valves actuated by mechanical or pneumatic actuators accordingly may require an actuator of a size incompatible with the space available. In the past, valve plug members have been coated to provide a lubricated surface between a valve housing surfaces and the movable plug member. Such reliance on a surface applied lubricant encounters the risk of contaminating a fluid flow through the valve.
U.S. Pat. Nos. 4,705,075 and 5,037,067 issued to one of the present inventors are of interest in that they disclose plug valves for use in high pressure systems.